Receiver for receiving radio waves from satellites

• US 6,373,431 B1
• Filed: 05/24/2000
• Issued: 04/16/2002
• Est. Priority Date: 05/27/1999
• Status: Expired due to Term

• Current Assignee: Casio Computer Company Limited
• Original Assignee: Casio Computer Company Limited
• Inventors: Nakajima, Shuuji
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US09/577,862
• Time in Patent Office: 692 Days
• Field of Search: 342/357.15, 342/357.13, 342/357.06, 701/213
• US Class Current: 342/357.66
• CPC Class Codes: G01S 19/24 Acquisition or tracking or demodulation of signals transmitted by the system synchronisation aspects of direct sequence spread spectrum modulation H04B1/7073
• CPC Class Codes: G01S 19/35 Constructional details or hardware or software details of the signal processing chain

Abstract

In a position measuring receiver, when ephemeris data is acquired from radio waves received from satellites in the measurement of a present position of the receiver, the acquired ephemeris data and data on a time when the ephemeris data was acquired are stored (steps SA6-SA8). Then, a time elapsed since the ephemeris data was acquired is calculated at intervals of one minute (steps SA10-SA12). After the elapsed time is more than two hours, an alarm is sounded at intervals of two minutes (steps SA13-SA14) to urge a user to acquire new ephemeris data at a spot suitable for receiving radio waves from the satellites before an effective term of the old ephemeris data is expired.

Claims

1. A portable receiver for receiving radio waves from satellites, comprising:

measuring means for receiving radio waves from the satellites so as to measure a present position of the portable receiver;

a memory for storing ephemeris data acquired from the received radio waves and used for measurement of the present position of the portable receiver by said measuring means;

determining means for determining a time elapsed from when the ephemeris data was acquired;

reporting means for reporting to a user a necessity for acquiring new ephemeris data; and

control means, responsive to the elapsed time determined by said determining means exceeding a preset time value, for causing said reporting means to report to the user; and

an instruction unit adapted to enable the user to instruct acquisition of the new ephemeris data.

2. The receiver according to claim 1, wherein said control means causes said reporting means to report to the user at intervals of a predetermined time after the elapsed time has exceeded the preset time value.

3. The receiver according to claim 1, wherein said control means causes said reporting means to stop reporting to the user during the measurement of the present position of the portable receiver by said measuring means.

4. The receiver according to claim 1, further comprising a destination memory for storing a destination specified by the user, and wherein said control means changes a type of reporting by said reporting means after a distance between the present position of the portable receiver measured by said measuring means and the destination stored in said destination memory becomes not more than a predetermined distance.

5. The receiver according to claim 1, further comprising urging means for urging the user to acquire the new ephemeris data after the elapsed time determined by said determining means has exceeded the preset time value during the measurement of the present position of the portable receiver by said measuring means.

6. The receiver according to claim 1, wherein said measuring means comprises means for acquiring the ephemeris data, and wherein said control means comprises means, responsive to the elapsed time determined by said determining means exceeding the preset time value, for causing said measuring means to continue to measure the present position of the portable receiver until the user performs a predetermined operation for confirming that the elapsed time has exceeded the preset time value.

7. A receiver for receiving radio waves from satellites, comprising:

calculating means for receiving the radio waves from the satellites so as to calculate a present position of the receiver;

a memory for storing data on the satellites acquired from the radio waves and used for calculating the present position of the receiver by said measuring means;

determining means for determining a time elapsed from when the satellite data was acquired;

reporting means for reporting to a user a necessity for updating the satellite data;

control means, responsive to the elapsed time determined by said determining means exceeding a preset time value, for causing said reporting means to report to the user; and

an instruction unit adapted to enable the user to instruct acquisition of updated satellite data.

8. A position measuring apparatus comprising:

calculating means for receiving radio waves from satellites and for calculating a present position of the apparatus;

a memory for storing ephemeris data obtained from the radio waves and used for calculating the present position of the apparatus, and a time at which the ephemeris data was acquired;

a timer for counting a present time;

determining means for determining a time elapsed from when the ephemeris data stored in the memory was acquired, based on the time at which the ephemeris data was acquired and the present time counted by said timer;

reporting means for reporting to a user a necessity for acquiring new ephemeris data;

control means, responsive to the elapsed time determined by said determining means exceeding a preset time value, for causing said reporting means to report to the user; and

a switch unit adapted to enable the user to instruct reception of the new ephemeris data.

9. A satellite data receiving method comprising:

calculating a time elapsed from when ephemeris data stored in a memory was acquired;

determining whether or not said elapsed time exceeds a preset time value;

notifying a user when the elapsed time exceeds said preset time value; and

acquiring new ephemeris data using a satellite data receiving unit when a user provides an instruction to receive said new ephemeris data.